Rotary finishing tool



Sept. 1, 1970 J. H. LEE 3,526,065

ROTARY FINISHING TOOL Filed Sept. 26, 1967 2 Sheets-Sheet 1 INVENTOR. J4M55 )9 lie Sept. 1, 1970 J, E 3,526,065

ROTARY FINISHING TOOL Filed Sept. 26, 1967 2 Sheets-$heet 2 INVENTOR.

United States Patent 3,526,065 ROTARY FINISHING TOOL James H. Lee, 2924 W. 234th St., Torrance, Calif. 90505 Filed Sept. 26, 1967, Ser. No. 670,537 Int. Cl. B24d 13/14 US. Cl. 51-358 5 Claims ABSTRACT OF THE DISCLOSURE Rotary disk tool for sanding, polishing etc. Rigid metallic driving hub has shank at one end to attach power source and peripheral socket at other end. Disk has connector shell centered on rear face. Shell fits into peripheral socket and has free end shaped to be driven by inner or outer wall of socket. In preferred form, has inward flange of hexagon shape to fit and be driven by center post of socket. Detent balls move radially outward of post to block disengagement of shell and fly-off. Safety lock is not affected by driving load.

BACKGROUND OF THE INVENTION This invention lies in the field of rotary finishing tools such as disk type sanders, buffers and polishers, and relates to structure for releasable connection of disposable finishing units to permanent re-usable rotary driving units. It is directed more particularly to driving and driven units of maximum simplicity in which the driving connection is positive in both acceleration and deceleration modes to eliminate any initial fly-off tendency, and an independent safety lock is provided which positively prevents inadvertent disengagement and is not affected in any way by driving loads. While the problems encountered are of the same general nature with all types of rotary finishing tools, they are generally most severe with sanding or abrasive disks because of the severe loading in use. Thus, although the description will make reference primarily to rotary abrasive tools, it will be understood that the problems and solutions are basically the same in all cases.

There are various types of rotary abrasive tools presently in use and they all perform their primary functions in a very satisfactory manner. However, they all have disadvantages which are traceable to the type of connection between the permanent driving unit and the disposable abrasive unit.

In one type, the abrasive disk is bonded to the driving pad with a cement which releases when the disk is deliberately peeled away beginning at one edge, or when a suitable solvent is applied. This is a rather ineflicient arrangement because it involves a great deal of down time for applying and removing each disk when replacement is required. Moreover, the heat of friction often causes the bonding agent to release, and the centrifugal force resulting from the high rotational speed will cause the disk to fly in any direction, often causing injury to personnel and damage to structural elements.

In another type, the disk is provided with slots, holes, or the like at its center for attachment to fingers, hooks, or bosses on the driver. When this type is subjected to conditions of extreme flexing or high torque resistance, the disk frequently fails or tears in the hub area, and flies off with great force to cause injury or damage.

In a third type, the disk has a plastic or flexible metal connector bonded to its rear face and configured to snap into a mating receptacle in the driving pad or hub. The complementary portions serve to drive the disk in rotation and to hold it in the hub by friction. When a large area of the disk is in engagement with a surface being finished, the connection is generally satisfactory. However, it is often necessary to apply high pressure at the extreme 3,526,065 Patented Sept. 1, 1970 margin of the disk, as in sanding inside radiused surfaces. In such case, the rearward flexing of the disk margin produces tension at the center and the connector frequently snaps out of the hub socket, with the usual dangerous consequences.

In still another type, the disk has a connector portion which may be a part of the disk backing or an attached piece. The connector and the driving hub have inter engaging hooks and slots which may be spring loaded to some extent. In any case, they are held in engagement primarly by the rotational torque of the driver. When the power source is turned off, the driver decelerates rapidly but the inertia of the disk tends to cause it to continue to rotate at high speed. The result is that the hooks become disengaged from the slots and the disk flies off in the same way as in the other forms mentioned above.

SUMMARY OF THE INVENTION The present invention provides a very simple, durable, and completely reliable rotary driver and rotary driven disk together with connecting means, which solve the problems mentioned above. Moreover, it provides for instant and effortless connection and release of the abrasive disk when it is necessary to intentionally make a change.

Generally stated, the tool includes a rotary driver and a rotary abrasive or other finishing disk, the driver having a socket to receive a connector secured to the rear side or face of the disk, and further provided with means to positively lock the parts against inadvertent relase. The driver is similar to prior devices to the extent that it has a central hub member or mandrel of rigid metallic material such as steel having a shank at one end to be gripped by a drill motor or other power source and having a socket at the other end. Surrounding the socket end of the hub is a pressure pad of resilient material such as rubber which tapers to a fairly thin and yieldable annular margin to back up the margin of the abrasive disk.

The center post of the hub serves as a first socket portion, and a sleeve surrounding and spaced from the post serves as a second socket portion. Between them they define an open ended peripheral socket having a closed bottom or inner end. The abrasive disk is provided with a connector in the form of a rigid metallic hollow shell coaxially secured to the rear face of the disk. In the preferred form the free end of the shell is formed with an inward flange defining a hexagon or other non-circular opening. For assembly the free end of the shell is slipped axially into the socket, and the flange opening engages a similar external formation on the post to form a driving connection.

To accomplish positive but releasable looking, the center post is hollow and carries detents in its wall, preferably steel balls, which are adapted to move radially outward in their mounting openings to effectively enelarge the diameter or lateral extent of the post and block removal of the shell by their interference relation. The detents are extended by engagement with a plunger which moves axially in the hollow post in response to spring pressure. The detents, and hence the shell, are released by fingertip movement of an external release collar against the spring action. With this arrangement the locking function is entirely independent of the driving function.

The connector shell may be modified to have a hexagonal or other non-circular cross section throughout part or all of its length, and the first or second socket portions or both may have a similar configuration throughout part or all of their lengths to serve as driving connections. If the shell is formed without an inward flange the detents may be forced into the radial high pressure engagement with the inner wall of the shell by a wedge formation on the plunger. In any of these modifications, the locking function is independent of the driving func- 3 tion. Therefore, it is not affected in any way by application or cessation of torque loads. Since the lock is positive it readily resists all tension type separating forces such as those resulting from flexing pressure on the disk margin. At the same time it is instantly releasable upon withdrawal of the locking plunger.

BRIEF DESCRIPTION OF THE DRAWINGS Various other advantages and features of novelty will become apparent as the description proceeds in conjunction with the accompanying drawings, in which:

FIG. 1 is a perspective view showing the tool of the invention mounted in a drill motor or other source of power;

FIG. 2 is an elevational view, partly in section, of the rotary driver with the rotary finishing disk mounted in place, and the means for locking the parts in assembled relation;

FIG. 3 is a side elevational view of themandrel portion of the driving hub;

FIG. 4 is an end elevational view of the mandrel;

FIG. 5 is a plan view looking at the rear face of the finishing disk with its connector;

FIG. 6 is a perspective view, partly broken away, of the preferred form of the connector;

FIG. 7 is a perspective view of a modified form of connector; and

FIG. 8 is a partial sectional view of a modified form of driving hub and lock means with a connector mounted in place.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The manner of use of the rotary finishing tool is illustrated in FIG. 1, in which a power tool is provided with a rotatable chuck 12. The finishing tool 14 is mounted in chuck 12 by its drive shaft and rotates as a unit, usually in a clockwise direction as indicated.

The sectional view in FIG. 2 shows all of the elements making up the total assembly ready for attachment to the power tool as in FIG. 1. The driving hub 16 includes a rigid metallic mandrel 18, rotatable about its central longitudinal axis, a first end of which is in the form of a solid shank 20 adapted for mounting in chuck 12. The central portion 22 and second end portion 24 are hollow and define a longitudinal passage 26 which houses a compression spring 28 and a slidable plunger 30 urged by the spring toward the open second end 24.

The mandrel is shown separately in FIGS. 3 and 4, where it will be seen that the central cylindrical portion 22 is pierced by a pair of radial access holes 32 for a purpose to be described. The second end portion 22 is formed with serrated annular boss or shoulder 34 for positive connection to a second part of the driving hub. The intermediate part of end portion 24 is provided with a hexagonal formation 36 which serves to drive the finishing disk. The hexagon shape is preferred but other non-circular shapes may be used if desired. The free end of portion 24 is formed as a cylinder 38 of the same size or slightly smaller than the distance across flats of hexagon 36. This cylinder serves as a guide for mounting the finishing disk. A pair of diametrally opposed radial openings 40 are formed in the hexagon section to slidably receive detent means.

Returning to FIG. 2, the mandrel requires an addi tional member to complete a driving hub having means to receive the connector of a finishing disk. For this purpose a sleeve 42 is provided in the form of a cylinder having an inwardly extending annular shoulder 44 to butt against shoulder 34 and space the sleeve radially from end 24. The inner end of the sleeve is force fitted over serrated shoulder 34 to lock it against relative rotation and is swaged inwardly at 46 to lock the two parts in assembled relation.

In the relation described, the end 24 of the mandrel constitutes a hollow central post or first socket portion and the forward free end of sleeve 42 constitutes a second socket portion radially spaced from the first portion to define between them a peripheral socket 423 which is open at the free ends of members 24 and 42 and closed at its inner end by shoulder 44. The outer wall of the socket, formed by sleeve 42, is cylindrical and the inner end of the inner wall is hexagonal or non-circular as defined by formation 36. A conventional pressure pad 70 of resilient material such as rubber is bonded to sleeve 42 and yieldingly supports the abrasive disk when it is pressed against the work piece.

The preferred form of finishing disk assembly is shown in FIGS. 2, 5, and 6, where it is seen to comprise a sanding disk 50, a backing 52, and a connector 54. The latter comprises a cylindrical shell 56 having an outwardly directed flange 58 at a first end and an inwardly directed flange 60 at its second, free end. Flange 60 is pierced to provide an opening 62 of hexagon shape to slide over and match the formation 36 to provide a rotary driving engagement. While the two matching forms are preferably hexagonal, they may be any other suitable noncircular shape if desired.

To make up the disk assembly, connector 54 is centered precisely on the back of abrasive disk with flange 58 in facewise relation after a suitable adhesive has been applied to the back of the disk. Backing 52 is apertured to clear shell 56 and coated with cement, after which it is placed in overlying relation with flange 5'8 and disk 50 and the cement is cured to bond them together permanently. Openings 64 may be formed in flange 58 to be filled with cement which will serve as rotary driving keys. Since the assembly is a throw-away" item there is no need to use cement which will allow peeling and might separate under the heat of friction. Instead, any one of many suitable cements is used which will not deteriorate at any temperature encountered in use.

To assemble the parts of the tool, connector 54 is brought into juxtaposition with the center of the driving hub and is guided into socket 48 by engagement of the cylindrical end 38 of the hollow post 24 within hexagonal aperture 62. The connector may then he slipped axially into full engagement with the socket with slight angular adjustment to match the hexagonal parts 36 and 62. The unit is now in the relation shown in FIG. 2, with the driving elements in engagement and with pressure pad 70 in contact with the back of the disk. Any rotary movement of the mandrel will be applied directly to the disk through the connector and all parts will rotate as a unit.

It will be noted that since flange is directed radially inwardly there is a substantial peripheral gap between hollow post 24 and the inner wall of shell 56. In order to lock the disk in the driver, detents which are preferably steel balls 66 are mounted for radial movement in openings 40 in the wall of the hollow post. The forward free end of plunger 30 is formed with a first steppeddown cylindrical section 68, a cone section 72 and a further stepped-down cylindrical section 74.

When the plunger is fully retracted against spring 28, section 74 is in radial alignment with balls 66-, allowing them to retract well into the post. As the plunger is extended, the cone section 72 moves them radially out into the gap and cylindrical section 68 holds them positively in this position where they increase the effective lateral dimension of the post and are in interference relation with the shell. Since they block outward movement of flange 60 they serve as a positive lock to prevent inadvertent disengagement of the finishing disk from the driver in the absence of absolute failure of some part. When a change is called for, finger tip release is accomplished by rearward sliding movement of collar 76 which is connected to plunger 30 by pin 78 which is axially movable in radial access holes 32.

A modified form of connector 80 is shown in FIG. 7, Where the shell 82 is formed with a hexagonal cross section and has no inward flange at its inner free end. The outwardly extending flange 84 which is to be bonded to the disk is provided with cutouts or openings 86 to receive cement serving as rotary driving keys.

The hollow center post 88 and sleeve 90 of FIG. 8 are basically similar to the corresponding parts of the driving hub of FIG. 2 but are modified to receive connector 80. The inner wall of sleevee 90 is preferably hexagonal to snugly receive shell 82 in rotary driving engagement. The outer wall of post 88 may likewise be hexagonal for driving engagement but may be cylindrical if desired. Balls 66 move radially in openings 92 as in the previous embodiment. However, since shell 82 is not provided with an inward flange at its free end, the balls must be pressed forcefully into engagement with the inner wall of the shell to produce an interference relation. To this end, plunger 92 is provided at its free end with a cone surface 94 having a slight slope to give a very high mechanical advantage. When the plunger moves forward the balls are pressed outward with a very high force and their very small area of contact results in a very high unit pressure and binding engagement. The net result is that the locking effect is positive, and inadvertent release is impossible. Those parts of the driver not shown are the same as those of FIG. 2.

Either of the connectors of FIGS. 6 and 7 may be provided with cutouts 64 or 86 or other suitable forms or may have no cutouts whatever in some cases. Shell 56 may be made hexagonal, as shell 82, and the latter may be formed with holes or depressions in its walls to receive balls 66, which would provide an even more positive lock. Also, the inner wall of sleeve 42 may be hexagonal the same as sleeve 90, and post 24 may be hexagonal throughout its length.

It will be apparent to those skilled in the art that various changes may be made in the device as disclosed without departing from the spirit of the invention, and it is intended that all such changes shall be embraced within the scope of the following claims.

I claim:

1. A rotary finishing tool comprising: a rotary driver adapted for connection to a rotatable power source, and a rotary finishing disk adapted to be releasably attached to said driver; said driver including a first rigid metallic socket portion having a central longitudinally extending axis of rotation, and a second rigid metallic socket portion coaxial with and surrounding said first portion in spaced relation to define between them an axially directed peripheral socket; said disk having a first face adapted for rubbing contact with a surface to be finished; and a connector in the tom of a rigid metallic hollow shell concentric with the disk and having a first end permanently secured to the second face of the disk and a second free end; said shell being proportioned to slide axially into said socket; at least a portion of said shell being non-circular and at least one of said socket portions having a corresponding formation to provide a rotary driving connection between the driver and the disk; said first socket portion having at least one detent means movable radially outwardly into interference relation with said shell to prevent axial movement of said shell and disengagement from the socket; and means carried by said first socket member and movable in a first direction to move said detent means to interference position and hold it in such position, and movable in a second direction to release said detent means for disengagement of said shell from said socket.

2. A tool as claimed in claim 1; said first socket portion being in the form of a hollow post defining an axial passage; and a plunger slidable in said passage; one end of said plunger being formed to urge the detent means radially outward in response to axial movement of the plunger.

3. A tool as claimed in claim 1; the free end of said shell being formed with a radially inwardly directed flange to surround and engage said first socket portion; said detent means in its interference position lying immovably in the path of movement of said flange to prevent disengagement of said shell from said socket.

4. A tool as claimed in claim 1; the movable means carried by said first socket member being adapted to force the detent means radially outward into high pressure binding engagement with the inner wall of said shell to prevent axial movement of said shell in said socket.

5. A tool as claimed in claim 1; the free end of said shell being formed with a radially inwardly directed flange to surround and engage said first socket portion; the inner margin of said flange being non-circular; and at least the inner end of said first socket portion having a corresponding formation to provide a rotary driving connection between said shell and said first socket portion.

References Cited UNITED STATES PATENTS Re. 26,552 3/1969 Block 51-358 2,764,853 10/ 1956 Rhees 51376 2,800,752 7/1957 Short 51-376 2,838,266 6/1958 Rees.

3,376,675 4/1968 Hutchins 5l-376 3,270,467 9/ 1966 Block 51358 LESTER M. SWINGLE, Primary Examiner D. G. KELLY, Assistant Examiner 

